Stereomicroscope

ABSTRACT

A stereomicroscope has a left and a right stereo radiation path and an adjusting device for selecting a stereo base. A main lens is arranged between an object to be observed and the adjusting device, which may be designed as an opto-mechanical switching device. The arrangement allows an integrated structure with low light losses.

This application is a divisional of application Ser. No. 09/237,839,filed Jan. 27, 1999 now U.S. Pat. No. 6,069,733; which is in turn aContinuation of application Ser. No. 08/718,451, filed Nov. 27, 1996,which is now U.S. Pat. No. 5,867,309, which is the national phase ofPCT/EP95/01186 filed Mar. 29, 1995.

BACKGROUND

The invention relates to a stereomicroscope.

Stereomicroscopes having a capability for adjusting the stereo base aredescribed in U.S. Pat. No. 3,818,125 (Butterfield, 1971). Althoughdifferent variations of possibilities for varying the stereo base aredescribed there, such devices have not become widespread in practice.This is in spite of the fact that the disadvantages which are known andspecified by Butterfield in the case of stereomicroscopes without stereobase adjustment are still present. To this extent, reference is made tothe relevant description parts—in particular in column 2, lines 43-62—inButterfield, which count as disclosed herein. The reason for not usingthe teachings of Butterfield apparently lies in various problems whichresult from his solution proposals. Thus, for example, the use of prismsis excluded (e.g. FIGS. 5-9 in Butterfield), since, as Butterfieldhimself admits (column 9, lines 65 and 66 of Butterfield), these areaccompanied by color aberrations which can have a negative influence onthe color quality of the viewed image. The variations proposed byButterfield having displaceable aperture diaphragms (10, e.g. FIGS. 2and 5) furthermore have the disadvantage that as a result of adisplacement of the latter not only is the stereo base adjusted but inaddition the image brightness is darkened or changed, which candisadvantageously lead to too low a light yield, in particular in thecase of small stereo bases.

Similar disadvantages occur in the case of the solution proposal inaccordance with FIG. 10 of Butterfield. To be specific, as a result ofthe pivoting of the mirror (50), not only is the stereo base adjusted,but the aperture is also changed, which in turn can lead tocorresponding light losses.

The variants proposed by Butterfield according to FIGS. 11 and 12 are inturn complicated and can be implemented only with difficulty to theextent that two parallel lens systems (54) are necessary there, whichare associated with a corresponding increase in price and also acorresponding increase in constructional size, with further penalties interms of light as a result of possibly too small an aperture.Furthermore, it is generally also difficult to adjust such parallel lenssystems such that they have identical properties. However, if theproperties are not identical, this can lead to fatigue in the observer,in particular if a video camera and monitor are connected in front ofsaid observer, since he does not have the possibility of recorrectingindividually, as in the case of two eyepiece beam paths.

It is therefore an object of the present invention to develop a systemwhich, in spite of a variable stereo base, does not reduce the lightintensity in the beam path—at least for a certain period and for eachbeam path separately—by a significant amount. In addition, it isintended to enable recordings—as known per se—using only a single imagerecording device, for example using a single video camera. Preferably,it is furthermore intended to provide only one main objective and torestrict the constructional size of the stereomicroscope to a minimum.

This object is achieved, for example, by means of the features describedherein. As a result of the arrangement of the adjusting device behindthe main objective, there is an integrated construction with low lightlosses and without the disadvantages listed above.

A practical application of the invention results, for example, in thecase of video stereomicroscopes.

For such microscopes, but also for other microscopes, a specialdevelopment of the invention is proposed which can also be appliedindependently of the invention. To explain the background:

Microscopes often have beam splitters in order to duplicate the beampath directed towards the object to be magnified.

Often provided on split beam paths are, inter alia, additional observereyepieces, phototubes, camera connections or displays of all types, theimages from which are intended to be inserted—that is to saysuperimposed on the image of the viewed object. This applies inparticular also to stereomicroscopes which have an image recordingdevice for producing a stereo view on a 3D display—possibly remote fromthe microscope.

For the last application, from time to time such an image recordingdevice (e.g. a CCD each) is provided both for the beam path assigned tothe left eye and also for the beam path assigned to the right eye.

For the application having the inserted display, in an analogous mannera display (e.g. a CRT each) is provided for the beam path assigned tothe left and also to the right eye.

These known stereomicroscopes thus have the disadvantage that twomagnification devices (zoom, turret) and two image recording devices ortwo displays, together with appropriate optics, are necessary. In thiscase, the left and right image recording devices or optics must bemutually adjusted.

In other known stereomicroscopes there are also solutions having only asingle image recording device. There, both the left and the right beampath or the ray bundle located in them are alternately fed to the singleimage recording device. As a result of such a construction, a secondimage recording device is saved and, inter alia, the serial recording ofa stereoimage pair on one video recording device is facilitated. Thechangeover process between the two beam paths is in this case achievedusing beam splitters and shutters which block off the respectiveundesired bundle of rays via polarization changes using correspondinglyarranged analyzers.

Such a stereomicroscope having geometric superimposition of the rightand left frames is described, for example, in U.S. Pat. No. 5,007,715.

The system which is described in U.S. Pat. No. 5,007,715 has thedisadvantage that, both during the polarization (about 50%) and duringthe superimposition (about 50%) of the two polarized bundles of rays bymeans of a beam splitter, up to 80% of the light intensity which ispresent of the respective bundles of rays (100%) are lost. A partialsuperimposition of the two different sets of image information from theright and left image beam paths can make itself noticeable as a furtherdisadvantage if the darkening by the analyzers is not 100%, which canprimarily also occur if the polarizers do not operate satisfactorily.Since however it is precisely in microscopes that the brightness on theobject to be viewed cannot be arbitrarily increased, the permanent lossin light intensity is disadvantageous. The partial superimposition, onthe other hand, can lead to unnecessary stresses for the organs of sightof the observer.

A similar known system is described in U.S. Pat. No. 5,003,385, wherelikewise about 80% of the light intensity of the left and right beampaths are absorbed before the light is incident on the single camera.

A somewhat different system, where the polarization of the light remainsunconsidered, is described in U.S. Pat. No. 5,028,994. There, the lightfrom two first beam paths (left and right beam path) is firstly fed ineach case to an LC shutter (twisted nematic type), which can open orclose the relevant beam path. The two beam paths are incident—deflectedvia mirrors—on a beam splitter. If one shutter is open, then the secondshutter is closed, for which reason theoretically it is always onlypossible for light from one of the two first beam paths to arrive at thecamera arranged downstream of the beam splitter. At the beam splitter,in each case about 50% of the light intensity is lost; likewise at theshutter, even in the “open condition”, about 50% in each case is lost,since the described shutter structure (cf. column 2 line 48 to column 3line 29) permit only light of a specific polarization direction to passthrough. In addition, in the case of the described shutter, theabovementioned disadvantages of partial superimposition may also occur.

SUMMARY OF THE INVENTION

It is therefore an object of the present development to develop a systemwhich reduces the light intensity in the beam path—at least for aspecific period and separately for each beam path—in the case of usingbeam splitters at a maximum to the extent of the light intensity lostthere (as a rule about 50%). In other words: a gain of about 50% of thelight intensity—both in the case of recording and in the case of theinsertion of images—is intended to be possible by contrast withconventional stereomicroscopes, although only a single image recordingdevice or only a single display is provided for both beam paths.Furthermore, the superimposition between the right and the left imagebeam path is intended to be excluded.

This additional object is achieved by means of features described below.The same problems or the same objects for microscopes having images tobe reflected in instead of images to be recorded are also solved for thefirst time.

For the specific further processing of video images which have beenobtained using a video stereomicroscope according to the invention,reference is made to the PCT patent application, having priorities ofthe three applications CH3890/93-3; CH135/94-3 and CH198/94-5 (now U.S.Pat. Nos. 5,870,137 and 6,040,852), which also count as lying within thescope of this disclosure. All the applications mentioned together, andthe inventions on which they are based, are symbiotically complementaryin the case of corresponding exemplary embodiments.

The geometrical superimposition of a left and right stereobeam path thenenables the recording of the two beam paths by only one video camera,with the result that images located alongside one another can berecorded successively in time and further processed. This develop- mentof the invention thus also enables the reproduction of images via onemonitor, as described for example in U.S. Pat. No. 5,007,715. Thestatements disclosed in relation to the figure in the abstract alsocount as disclosed herein.

The use according to the invention of mechanical aperture diaphragmswhich either completely reflect light or allow light to pass throughcompletely, has the effect, at least during the respective duration of aspecific switching position of the aperture diaphragm, of forwarding thecomplete light intensity of the light located in the relevant beam path.The encoding process for the light, such as for example in the use ofpolarization, as also proposed by Butterfield, is therefore dispensedwith. In this case, only insertion or blanking out is used. This resultsin a gain in intensity of up to over 200%, compared with knownarrangements having splitters and polarization filters. An undesiredsuperimposition of two beam paths is excluded—advantageously by contrastwith the use of polarization. As a result of this development of theinvention, in addition the further object is thus achieved of effectinga light intensity loss which is only low, in spite of geometric beamsplitting.

Although the use of mechanical aperture diaphragms in opticalsystems—even if for completely different purposes—is known in principle,thus, for example, reference is made to a Nipkow disk, such as isrepresented for example in U.S. Pat. No. 5,067,805, or to rigidmechanical beam splitters in which, for example part of the light in thebeam path is allowed through at an annular aperture diaphragm andanother part is reflected back for beam splitting, these knownmechanical beam splitters do not reduce the actual light intensity loss,since following the splitting, in each subsequent beam path in each caseonly part of the original 100% light intensity is forwarded. The otherpart is in fact deflected further by the splitter into the second beampath.

Individual applications having monochromatic light could reducesplitting losses at splitters to a residual, which however is notpossible if it is desired to use the entire light spectrum.

A partial aspect of the invention is therefore found in the case of amicroscope, in particular a stereomicroscope, having a first beam pathand a beam splitter in this beam path, the beam splitter being designedas a mechanooptical or electrooptical switching element which can betransferred alternately from a reflective into a transmissive or anotherreflective state, one of the two states exposing the light path for thefirst beam path and the other state exposing the light path for a secondbeam path, while blocking the light path for the viewing beam path. Sucha switching element thus replaces conventional beam splitters, by whichmeans the light loss can be reduced significantly.

Within the scope of the invention there are various further types ofdesign and variants thereto, which are described below.

In the case of a preferred variant, the entry bundles of rays of thestereomicroscope are geometrically superimposed—but chronologically oneafter the other—after the (single) main objective, either by means of arotating mirror having at least in each case one transmissive andreflective subregion or by means of a stationary splitter and a rotatingaperture diaphragm which alternately covers the entry beam paths. Inthis case it is favorable if both beam paths have the same optical pathlengths as far as the image recording device. In the sense of theinvention, it is in this case not important in which form the reflectingaperture diaphragms are introduced. Translatory movements are in thiscase to be equated with rotating movements or other switching movements.Thus, for example, it is thus entirely possible to provide aperturediaphragms similar to photographic camera shutters, but which areappropriately silvered on at least one side. A variant havingmicro-mechanical lamellar mirrors is likewise conceivable, such lamellarmirrors—at present these are essentially only in laboratoryexperiments—being generally constructed from silicon and being switchedby means of electrostatic charges.

If, as in one exemplary embodiment, a rotating glass disk is used whichis silvered on one half, a practical, easily balanced arrangement isgiven thereby, which however has one small disadvantage; on thenon-silvered glass half, because of the plane plate effect, an imageoffset occurs. In order to avoid this, in the case of a preferredvariant, the glass is omitted at this point, so that a completely freelight passage is possible there.

In the case of all pushed-in or turned-in aperture diaphragms, since theeffect of the moving aperture diaphragm can be disadvantageous incertain circumstances for recordings on image recording devices, forexample CCDS, provision is further made in some embodiments for thedisplacement or rotational movement to be carried out particularlyrapidly and for the aperture diaphragm to remain in the switchingposition then assumed for a certain time. In the case of rotatingaperture diaphragms, a drive having a stepping motor is particularlysuitable for this. A corresponding addition or alternative for thistechnique results from a clocked exposure control of a video camerawhich is possibly being used, or a display which is being used.

If appropriate, additional light may be fed to the object via the saidsilvered surface via a further mirror arrangement. It might even bepossible, under certain circumstances, for other more complicatedillumination devices to be omitted as a result.

A further variant having a 50/50 pupil splitter is advantageous in asmuch as only one glass splitter per beam path is necessary and, in theeyepiece beam path, depending on the splitter effect of this glasssplitter, a ratio of, for example, 25% display and 50% object or (at theeyepiece) for example 50% display and 50% object can be achieved. Thefirst, for example, in the case of a glass splitter of about 1/1 partialeffect, the latter for example using a glass splitter of about 2/2partial effect.

A further variant, which integrates the illumination completely into thestructure, results if the switching element is used twice, in that thereflecting surface is used on both sides. In the pivoted-in state, itlies at the point of intersection of the axes of the first beam paths,preferably at an angle of 45° each to the said axes. Arranged in directprolongation of one of the first beam paths is a light source whoselight, in the pivoted-in state of the switching element, is reflectedinto the one beam path, whereas it falls directly into the other firstbeam path in the pivoted-out state. In this way, optimal illumination ofa viewed object is possible.

It is further preferred to place the aperture diaphragm or the splittermirror as close as possible to the main objective, in order to avoidvignetting of the reproduced images.

A variant having a plurality of circular segment-like reflectors reducesthe required number of revolutions of a rotating mirror.

The use of plane plates as a stereo base setting is constructionallysimple. The disadvantages of the use of prisms, as in Butterfield, areomitted thereby. The mechanical construction is simple to realize,miniaturization and any automatic and/or remote control is simple.Coupling to the magnification setting of the stereomicroscope and/or toa zoom setting is therefore conceivably simple. The light losses areminimum in contrast with the use of aperture diaphragms as inButterfield.

A special design of the invention serves to reflect in information foran observer of an eyepiece beam path. All the previously mentionedspecific and advantageous designs and variants can be used practicallyalso in conjunction with this structure.

If, in conjunction with such a stereomicroscope, in each case a rightand left frame of a stereoimage pair is displayed on the display, theobserver thus obtains a 3D image to view, which is superimposed on the3D image of the eyepiece beam path. Advantageously, it is possiblethereby for, for example, positron ray images or magnetic resonancestereoimages to be superimposed on the currently seen images. In thecase of the use of such stereomicroscope as a surgical microscope, thisresults in particular advantages for the surgeon, especially since hecan interpret the image seen in a better way. On the other hand, thereflected-in images could also contain other information, for exampleabout the control of devices or of the microscope itself. In thisconnection, reference is made to the following Swiss patentapplications, whose content likewise counts as disclosed within thescope of the invention: CH3890/93-3; CH135/94-3 and CH198/94-5 (now U.S.Pat. Nos. 5,870,137 and 6,040,852). A combination of the teachings ofthese applications with the present application is particularlypractical. In particular, a combination having mechanical beam splittersis preferred, since in this case a further light intensity gain of about100% (a total of about 200%) is possible.

It is of course possible for the variant with the image recording deviceto be used simultaneously with the variant having the display, providingthat a split-off beam path each is made available to both.

Instead of the mechanically moved aperture diaphragms, other types ofaperture diaphragms could also be used, provided that they are onlycapable of changing one hundred percent between a transmitting andblocking state.

The invention is described in particular in conjunction with astereomicroscope. In the widest sense, however, it can also bepractically used with any other beam paths.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and designs of the invention emerge from the drawings.In the figures shown there:

FIG. 1 shows the principle of a construction for stereo base settinghaving a rotating beam splitter with a mirror surface;

FIG. 2 shows the principle of a construction having a conventionaloptical nondisplaceable beam splitter which is preceded by analternating shutter element for beam separation;

FIG. 3 shows the principle of a rotating beam splitter with a mirrorsurface;

FIG. 4 shows a variant of FIG. 3;

FIG. 5 shows the principle of a construction in accordance with U.S.Pat. No. 5,007,715 with an adjusting device according to the inventionand only one main objective;

FIG. 6 shows the principle of a construction having an LCD shutterelement and two displaceable mirrors;

FIG. 7 shows the principle of a rotating beam splitter with a mirrorsurface;

FIG. 8 shows the principle of a translatably displaceable beam splitterwith a mirror surface;

FIG. 9 shows the principle of an electronically switchable LCD shutterelement, which can be switched over from a reflective into atransmissive state;

FIG. 10 shows the principle of a micromechanical lamella mirrorconstruction as beam splitter with a transmissive and a reflectiveposition;

FIG. 11 shows the principle with a micromechanical lamella mirrorconstruction as beam splitter with at least two reflection positions;

FIG. 12 shows the compensation of phase shifts on lamella mirrorsaccording to FIG. 11;

FIG. 13 shows a variant of FIG. 11, with equally long left and rightbeam paths and rotating switching element;

FIG. 14 shows a variant of the switching element according to FIG. 1, asused in FIG. 3;

FIG. 15 shows the principle of a microscope with reflection of 3D imagesand rotating switching elements according to the invention;

FIG. 16 shows a variant of FIG. 13 with splitter (4C) and switchingaperture diaphragms;

FIG. 17 shows switching element having at least two shutter lamellae;

FIG. 18 shows a variant of FIG. 15 with a display displaced to the side;

FIG. 19 shows a circuit for driving and synchronizing a mechanoopticalswitching element;

FIG. 20 shows a construction having integrated illumination through themain objective;

FIG. 21 shows an analytical listing of the high light losses caused byconventional technology 1) and a representation of the low light lossesas a result of the technology according to the invention 2), as well asthe advantage 3) resulting threfrom;

FIG. 22 shows the principle of a rotating aperture diaphragm made fromglass according to the invention, together with an image recordingdevice;

FIG. 23 shows the principle of a translatably displaceable aperturediaphragm for the same application according to FIG. 1;

FIG. 24 shows a variant to the construction according to FIG. 6 with apupil beam splitter;

FIG. 25 shows a further variant having an aperture diaphragm, mirrorsurfaces and stroboscopic illumination;

FIG. 26 shows a similar construction to that of FIG. 22, the stationarysplitter being replaced by a rotating splitter;

FIG. 27 shows the principle of a construction having a display for theinsertion of an image into the eyepiece beam path;

FIG. 28 shows a construction for reflecting in images from a display.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The figures are described as a coherent whole. Identical referencesymbols denote identical components. Identical reference symbols withdifferent indices denote similar or functionally similar components. Theinvention is not restricted to the exemplary embodiments shown. Aboveall in combination with the teachings of the Swiss patent applicationscited above and the US patents cited above, any further variants may berepresented. They all fall under the disclosure content of thisapplication.

FIG. 1 shows as a component 3 a a component as is described in moredetail in FIG. 7.

As an alternative, an element 3 d according to FIG. 6 or according toFIG. 9 of the last-named patent application may also be providedinstead.

FIG. 1 shows a stereomicroscope construction having two parallel firstbeam paths 1 a, 1 b along their central axes 7 a and 7 b, which are bothplaced through a main objective 8. The beam path 1 a is incident afterthe main objective on a deflecting mirror 19 which is held on a push rod20 and is set such that the central axis 7 a is directed somewhat intothe center of an image recording device 9 (CCD), which is arrangeddownstream of magnification optics 33 (zoom) and downstream of a tubelens 31. By means of displacing the deflecting mirror 19—via itsactuating drive 36—the stereo base d between the two central axes 7 aand 7 b is changed, without the central axis 7 a deviating from thecenter of the image recording device 9.

The other first beam path 1 b is likewise incident in the representationshown on a switching element 3 a or on a mirror, which is nonethelessdesigned on a semicircular disk 5 c, which can be rotated by a motorabout the axis 6 in accordance with FIG. 1. In the position shown, thebeam path 1 a to the image recording device 9 is blocked off thereby,while the beam path 1 b is reflected as beam path 2 onto the imagerecording device 9. The central axis 7 b of 1 b is in this case aimed atthe same point as the central axis 7 a. The two beam paths 1 a and 1 bare thus superimposed consecutively but geometrically on one another. Afurther mirror 35 can also be located between the switching element 3 aand the image recording device 9, in order to compensate the imagemirroring caused by the optical arrangement. The image recording devicewould then have to be accordingly pivoted upward offset by approximately90°.

The mirror on the semicircular disk 5 c is configured—if appropriatealso provided with curved boundary lines—in such a way that the read-outprocess is effectively synchronized to the image recording device 9(CCD).

As a result of this construction, the disadvantage in existingstereomicroscopes is avoided, which disadvantage results from thenormally fixed mechanical/optical spacing of the two beam paths 1 a and1 b. To be specific, this previously fixed the stereo base and, inconjunction with the focal length of the main objective 8, theconvergence angle of the stereoscopic beam path. The convergence angle,however, is again a decisive parameter of the depth magnification. Bymeans of this variant of the invention, a setting of the convergenceangle irrespective of the focal length of the main objective 8 is thuspossible in an advantageous manner. This results in a possibility ofcontrol of the depth magnification. This has the effect of a decisiveand ergonomic improvement to the stereoscopic perception of depth,without light losses occurring as in the case of Butterfield.

As can be seen symbolically better from FIG. 3, the semicircular disk 5c is silvered as switching element 3 a. The second part of the disk ismass-free, in order to avoid disturbances such as image offset or thelike. Mounted at the edge, simply as a mass balance, is a balancingweight 40, which is held in relation to the axis of rotation 6 by a thinbeam 37.

FIG. 6 shows a variant of FIG. 1 having equally long left and right beampaths 1 a and 1 b and an LCD shutter switching element 3 d. As analternative to FIG. 7, the latter could once more be designed on a thinglass disk 5—in accordance with FIG. 13. The image offset produced inthe region of the remaining surface 5 b is compensated in that in thiscase the mirror surface of the switching element 3 a is not produced onthat surface of the disk 5 facing the beam path 1 b but, in the case ofthe LCD shutter element, approximately in the center of the disk at theLCD elements located there. Both the beam paths 1 a and 1 b thus sufferan image offset in the same direction.

The significance of the beam paths 1 a and 1 b in the case of thearrangement in FIG. 6 is their identical length as far as the imagerecording device 9. This identical length is achieved by means of thesymmetrical construction about the central axis of the main objective 9,which is supported by two deflecting mirrors 11 a and 11 b. These couldalso be replaced by 30° prisms. The decisive factor is that they may bedisplaced (preferably simultaneously and to the same extent) along thearrow line shown.

Here, as also in the case of other designs, the mirror delivers, asalready mentioned, an optimum light intensity, since neither losses as aresult of polarization nor losses as a result of the use of a splitteroccurs. FIG. 6, like FIG. 1, shows a CCD camera as an image recordingdevice 9. However, this may also be designed as any other type of videocamera.

The drive of the disk 5 is intended to be synchronized with thereading-out of the image recording device 9. In this arrangement it isadvantageous if the reading-out of the image recording device 9 needsonly part of the time during which the mirror feeds one of the two entrybundles of rays to the device. The clock frequency for controlling thereading-out of the recording device is to be calculated from thisprescription and from the rotational speed of the aperture diaphragm (50Hz). (See FIG. 17).

The switching element 3 a, which is shown in FIG. 3, has a straightseparating line between the reflective and transmissive part. Thisseparating line can however be further optimized. FIG. 4 shows a variantof this having 3 reflective circular section areas 5 d, which allow areduction in the rotational speed of the switching element 3 a.

The image data obtained is further processed in accordance with thespecific patent applications.

In the sense of the invention, it is not important which of thepreviously described switching elements 3 is used, although a rotatingdisk is preferred. Furthermore, as an alternative, in accordance withFIG. 2 instead of a switching element, a conventional (for exampleglass) beam splitter 4 is also employed, an active alternating shutterelement 3 f as an aperture diaphragm then is being switched into thebeam paths 1 a and 1 b alternately, said element making either the oneor the other beam path 1 a or 1 b able to be passed. To this extent,reference is expressly made to FIGS. 22 to 28, which show appropriateaperture diaphragms.

Other variants have in each of the beam paths a plane plate which can bepivoted. A possibility for setting the stereo base d results from theoffsetting effect of the obliquely set plane plate. According to afurther variant, a pivoting drive is provided, which moves both theplane plates synchronously. For this purpose, the plane plates areconnected to the drive via a linkage. For specific electronic evaluationmethods—for example in order to achieve a pixel document—it is evenconceivable for the pivoting drive of the plane plates to be provided inan oscillating manner.

FIG. 7 shows a first beam path 1 having an optical axis 7 and containinga main objective 8 and an eyepiece 18. Located in this beam path 1, atan angle of about 45°, is a glass disk 5 which is rotatable about anaxis 6, and which has a semicircular area 5 a which is silvered facingthe objective 8. The semicircular remaining area 5 b is transparent. Asindicated symbolically, the disk 5 may be driven by an electric motor,for example by a stepper motor 14. When the area 5 a is in the beam path1, the latter is reflected into a second beam path 2, split offtherefrom. If, on the other hand, the remaining area 5 b is located inthe first beam path 1, the latter continues in a straight line freely asfar as the eyepiece 18. The disk 5 in this way becomes a mechanoopticalswitching element or a silvered aperture diaphragm 3 a.

FIG. 8 shows a variant of FIG. 7, in which, instead of the disk 5, anoscillatingly displaceable mirror is used as switching element 3 b. Thisis driven by a reciprocating drive 15.

FIG. 9 shows a further variant of FIG. 7 having an electricallyswitchable switching element (e.g. LCD) 3 d which, for example onaccount of liquid crystal changes, transfers from a transmissive into areflective state. It is controlled via feedlines 16.

FIG. 10 shows a further variant of FIG. 7 having a mechanoopticalswitching element 3 e, which is designed as a micromechanical lamellarmirror construction. The individual, symbolically indicated lamellarmirrors 30 are, as indicated by the arrows 34, pivotable such that theyin each case lie approximately parallel to the first beam path 1 or ineach case obliquely thereto. In the first case the beam path 1 iscontinuous, in the second case it is deflected into the second beam path2. The outermost right-hand lamellar mirror 30 is shown in thisposition.

FIG. 11 shows a further mechanooptical switching element 3 e, a, forexample, micromechanical lamellar mirror construction for setting atleast two lamella positions. Lamellae 30 are pivotable either about acentral axis each or about one longitudinal edge each of the relevantlamella (cf. the arrows indicated). By means of these lamellae 30,reflective switching between beam path 1 or 2 is possible.

FIG. 12 describes the compensation of phase differences of individualpart-waves 42 at lamellar mirrors 30, starting from a planar wave 41, ata phase plate 44, with result 43. This invention, shown in FIGS. 11 and12, may also be used independently.

FIG. 13 shows a variant of FIG. 1 having identically long left and rightbeam paths 1 a and 1 b and a rotating switching element 3 a. As analternative to FIG. 3, the latter is once more designed on a thin glassdisk 5—in accordance with FIG. 14.

One of the main features of the beam paths 1 a and 1 b in the case ofthe arrangement in FIG. 13 is their identical length as far as the zoom13 or as far as the image recording device 9. This identical length isachieved by means of the symmetrical construction about the central axisof the main objective 9, which is supported by two deflecting mirrors 38a and 38 b. The latter could also be replaced by prisms.

Here, as also in the case of the other designs, as already mentioned,the mirror supports an optimum light intensity, since neither losses asa result of polarization nor losses as a result of the use of a splitteroccur. FIG. 13, like FIG. 1, shows a CCD camera as image recordingdevice 9, but this could also be designed as any other type of videocamera.

The drive of the disk 5 (e.g. FIG. 14 and FIG. 13) is intended to besynchronized with the reading-out of the image recording device 9. Inthis case it is advantageous if the reading-out of the image recordingdevice 9 needs only part of the time during which the mirror feeds oneof the two entry bundles of rays to the device. The clock frequency forcontrolling the reading-out of the recording device is to be calculatedfrom this prescription and from the rotational speed of the aperturediaphragm. The necessary clock signals are advantageously extracted bymeans of various frequency dividers from the output signal of anoscillator, as can be seen from FIG. 19 (in this connection, referenceis expressly made to the Swiss patent application 135/94 and,respectively, to the PCT patent application based thereon, which givesinformation about the technique for video signal processing which isparticularly advantageously to be used within the scope of thisinvention; the appropriate statements about the storage technique of theframes or fields, respectively, or their conversion and display as araster image count as disclosed herein).

The switching element 3 a shown in FIG. 14 has a straight separatingline between the reflective and transmissive part. This separating linecan, however, be optimized further. Such an optimized separating linecan be found by means of experiments.

The image data obtained are further processed by means of a memory and aspecial read-out process, in order to reduce the flicker and themovement jitter in the stereo images reproduced. At this point it shouldbe noted that this flicker and jitter fundamentally occurs in allsystems in which the left and right frame are fed alternately to arecording device. The said read-out control is therefore able to be usednot only in the previously described system but in each device having ageometrical superimposition of the left and right frames. The read-outcontrol and the device for implementing this control for this reasonrepresent an independent invention which can be pursued further,irrespective of the use of the mechanical aperture diaphragms.

FIG. 15 shows a construction for reflecting images from a display 10 ainto two eyepiece beam paths 1 c and 1 d of a stereomicroscope. Thisconstruction—and also that of FIG. 18—could also be equipped with animage recording device instead of the display 10 a. Such an imagerecording device could optionally also be arranged above an additionalbeam splitter, in addition to the display 10 a. Here, too, prisms allowan identical beam path length. The likewise symbolically representedswitching element 3 a allows the transfer of successive images on thedisplay successively into the two beam paths 1 c and 1 d. Practicallyspeaking, the display is connected to electronics, not shown, which ineach case displays one of the successive images the wrong way round, inorder to be able to see two upright frames, the right way round, in thestereoscopic field of view of an observer.

FIG. 16 shows a variant of FIG. 13 having a rotating aperture diaphragm24 which, for the purpose of reducing the rotational speed, can forexample be designed in accordance with FIG. 17, and a splitter 4 c. Asan alternative, the aperture diaphragm 24 can also be equipped as aswitching element having at least two shutter lamellae—one for each beampath.

The construction in accordance with FIG. 18 is a variant of FIG. 15having two beam splitters 4 a and 4 b, one of which cooperates with arigid mirror 21 and the other with an electrooptical switching element 3of any configuration within the scope of the invention. The parts 21 and3 alternately expose the view of the display 10 a, the image from whichis superimposed on the eyepiece beam paths. In this case, this may be astereoscopic or else a monoscopic image.

The construction in accordance with FIG. 20 represents a solution havingintegrated illumination. A light source 17 is arranged in directprolongation of the beam path 1 b, and the switching element 3 a issilvered on both sides. In the position shown, the light from the lightsource 17 is reflected via the one mirror on the switching element 3 aand via the mirror 21 into the beam path 1 a. The light sourceilluminates the object 22 in this way, while said object or its frame issimultaneously recorded by the image recording device 9 via the othermirror on the switching element 3 a and via the beam path 1 bIf theswitching element 3 a is switched to transparency, the light source 17then illuminates the object via the beam path 1 b, while the other framecan be recorded via the beam path 1 a. The light source may also bedesigned as a stroboscope and can be clocked both with the imagerecording device and also with the switching element 3 a. As analternative or at the same time, measurements or insertions etc. mayalso be made via the illumination beam path 2 b.

In the sense of this construction it is not important which of theabove-described switching elements 3 is used, although a rotating diskis preferred. Furthermore, as an alternative, instead of a switchingelement a conventional (e.g. glass) beam splitter could also be used,active aperture diaphragms then having to be switched into the beampaths 1 a and 1 b alternately, said aperture diaphragms then makingeither one or the other beam path 1 a or 1 b continuous. To this extent,reference is expressly made to FIGS. 22 to 28, which describescorresponding aperture diaphragms. The construction in accordance withFIG. 20 or its variants could accordingly also be used independently.

It may be advantageous to use pellicles for the construction of therotating switching elements 3. These are frames on which virtuallyweightless films are clamped. On the one hand, these have, virtually nooffset and, on the other hand, they are very light, so that weightproblems are dispensed with.

The following designs, or FIGS. 22 to 28 respectively, are notrestricted to the exemplary embodiments shown. Above all in combinationwith the teachings of the Swiss patent applications cited above and theother figures, further arbitrary variants may be represented. Thus, asalready mentioned, not only rotating and translatory movements areconceivable for the aperture diaphragm, stationary electroopticalaperture diaphragms with a hundred percent switchover capacity andwithout light intensity loss in the continuous range are conceivable, asare mechanical aperture diaphragms which can be pivoted in and out.Mirrors used can in many cases also be replaced by similarly actingprisms. All these variants fall under the disclosure content of thisapplication.

FIG. 24 shows a construction for the recording of left and right framesof a stereoscopic beam path one after the other in a time sequence. Asin the construction according to FIG. 23 and FIG. 26, in this case theright and left beam path 1 a and 1 b are equally long. A rotatingaperture diaphragm 3 a makes them alternately continuous or blocking.Said aperture diaphragm is designed on a thin glass disk 5, for exampleby coating the disk approximately one half black and opaque 5 a (FIG.14). The image offset which is theoretically produced in the region ofthe completely transparent remaining area 5 b, (apart from anyreflection at the glass disk, which is preferably reduced by anantireflection coating) is compensated by the fact that, depending onthe position of the disk 5, it acts equally on both the beam paths 1 aand 1 b. The opaque area 5 a of the disk 5 is preferably also(or—providing the silvering is light-tight—only) silvered, in order toreturn light split off by it into the respective beam path 1 a or 1 b.

The beam paths 1 a and 1 b are in this arrangement in a favorable wayidentically long as far as the zoom 13 or, respectively, as far as theimage recording device 9. This identical length is achieved by means. ofthe symmetrical construction about the central axis of the mainobjective 9, which is supported by two deflecting mirrors 38 a and 38 b.The latter could also be replaced by, for example, 30° prisms.

The two mirrors 38 a and 38 b reflect the two beam paths 1 a and 1 b ata common beam splitter 50 a, by means of which they are superimposedgeometrically on each other. The loss of about 50% of the light energywhich generally occurs in so doing is the only light intensity lossoccurring in this system which must be tolerated. According to thedevelopment described further above, this loss may also be avoided if aswitching element 50 b (FIG. 26) is used in place of the beam splitter50 a, said switching element switching between a reflective and atransmissive state, as described at the corresponding places in theapplication mentioned. In the case of the invention represented,however, no light intensity losses occur as the result of a polarizer oranalyzer. FIG. 22, FIG. 23, FIG. 27 and FIG. 25 show a CCD camera asimage recording device 9. However, the image recording device 9 can alsobe designed as any other type of video camera.

The drive (motor 14) of the disk 5 is to be synchronized with thereading-out of the image recording device 9. It is advantageous in thiscase if the readingout of the image recording device 9 needs only partof the time during which the aperture diaphragm makes one of the twoentry bundles of rays available to the device 9. The clock frequency forcontrolling the read-out of the recording device 9 is to be calculatedfrom this prescription and from the rotational speed of the aperturediaphragm (e.g.: 50 Hz). The necessary clock signals are advantageouslyextracted by means of various frequency dividers from the output signalof an oscillator (clock), as can be seen from FIG. 19. A reduction inrotational speed can be achieved if, instead of an aperture diaphragmaccording to FIG. 3, an aperture diaphragm according to FIG. 4 isselected, whose three blocking areas are of circular segment design. InFIG. 25 it can be seen, indicated symbolically, that the correspondingdrives 14 for the rotatable disks are driven by a common controller 12,which also undertakes the clocking of the image recording device 9 andthe clocking of any stroboscopic illumination 17 a and 17 b.

Such a stroboscopic illumination is successfully used in thosearrangements in which the aperture diaphragm 3 a is additionallydesigned to be silvered. In the position of the aperture diaphragm 3 awhich is shown in FIG. 25, for example, the stroboscope lamp 17 b emitsa light flash which is reflected via the area 5 a into the beam path 1 band illuminates the object 22 in this way. At the latest following a 180degree rotation of 3 a, a light flash from the stroboscope lamp 17 ailluminates the object 22 via the beam path 1 a.

The switching element 3 a shown in FIG. 14 has a straight separatingline between the reflective and transmissive part. This separating linecan, however, be optimized further.

The image data obtained are, as indicated for example in FIG. 19,further processed by means of a memory and a special read-out process,in order to reduce the flicker of and the movement jitter in thereproduced stereo images. Here it should be noted that this flicker andjitter fundamentally occur in all systems in which the left and rightframes are alternately fed to a recording device. The said read-outcontrol can therefore be used not only in the previously describedsystem but in any device having a geometrical superimposition of theleft and right frames. The read-out control and the device forimplementing this control therefore represents an independent invention,which can be followed further irrespective of the use of the mechanicalaperture diaphragms.

FIG. 23 shows a variant of FIG. 22 in which, instead of the disk 5, anaperture diaphragm which can be displaced in an oscillating manner isused as switching element 3 b. The latter is driven by a reciprocatingdrive 15. In this case, the aperture diaphragm comprises two blockingareas 5 d and 5 e which, for example, are applied to a rectangular glassdisk in such a way that in the one position (shown) the beam path 1 a isblocked and in the other the beam path 1 b is blocked. Instead of aglass disk, such an aperture diaphragm 3 b could also be constructed,for example, from sheet metal, in which only the exposed regions of theaperture diaphragm are stamped out.

FIG. 9 of the Swiss patent application shows an electronicallyswitchable switching element (3 d) which, for example because of liquidcrystal changes, transfers from a transmissive into a reflective state.Two such elements could, for example, be inserted into the beam paths 1a and 1 b instead of the aperture diaphragms 3 a or 3 b, in order toblock the light transmissivity alternately in a corresponding manner.

As a further variant to 3 a and 3 b, the mechanooptical switchingelement 3 e, which is designed as a micromechanical lamellar mirrorconstruction according to FIG. 10, are conceivable, such a lamellarconstruction then preferably being placed into each beam path 1 a, 1 b.

FIG. 28 shows a construction for reflecting images from a display 10 ainto two eyepiece beam paths 1 c and 1 d of a stereomicroscope. 30°prisms allow an identical beam path length here, too. The likewisesymbolically represented aperture diaphragm 3 a allows the transfer ofsuccessive images on the display one after another into the two beampaths 1 c and 1 d. In a practical way, the display is connected toelectronics, not shown, which in each case displays one of thesuccessive images the wrong way round, in order to be able to see twoupright frames in the stereoscopic field of view of an observer.

The construction in accordance with FIG. 27 is a variant of FIG. 28having two beam splitters 50 a and 50 b, one of which cooperates with arigid mirror 21 and the other with a third beam splitter 50 a. Anaperture diaphragm 3 a according to the invention alternately exposesthe view of the display 10 a for the beam paths 2 a and 2 b, the imagefrom which display is superimposed on the eyepiece beam paths. In thiscase, this may be a stereoscopic or else a monoscopic image. In thelatter case, the aperture diaphragm 3 a may be dispensed with.

The construction according to FIG. 24 operates with a pupil splitter 19made of two deflecting mirrors 19 a and 19 b, each of which deflectshalf the image information, as it is supplied by the display 10 a, tothe beam path 1 a and 1 b, respectively. At the point of intersection ofthe beam paths 2 a and 2 b with 1 a and 1 b, beam splitters 50 a arearranged which allow the geometric superimposition of the two beam paths1 a and 2 a, and 1 b and 2 b, respectively. A rotating aperturediaphragm 3 a according to the invention alternately covers thecorresponding regions in front of the pupil splitter 19 a, so that ineach case only one of the two beam paths 1 a or 1 b is supplied with theimage information. If the display correspondingly switches in each casebetween a right and a left frame, a stereoscopic image, which issuperimposed on the 3D image from the beam paths 1 a and 1 b, isproduced for an observer at the eyepiece 18 a and 18 b. From thisconstruction, use of a second display 10 can be saved. Thestereomicroscope according to the invention is accordingly of smallerconstruction.

The last described development thus relates to a stereomicroscope inwhich two beam paths 1 a, b; 2 a, b are intended to be superimposedgeometrically but successively in time in a transparent manner. Theknown disadvantages, such as high light loss as a result of polarizersand analyzers or such as undesired simultaneous superimposition of imageinformation are intended to be avoided. This is achieved by means of amechanical aperture diaphragm 3 which either exposes the one or theother beam path 1 a, b; 2 a, b and blocks the respective other beampath.

 1a, b First beam path  1′ Displaced first beam path  2a, b Second beampath (geometrically superimposed first beam paths)  2′ Displaced secondbeam path  3 Mechanooptical switching element 3a, b, c Opaque andpreferably silvered aperture diaphragm 3d LCD shutter element 3eMicromechanical lamellar mirror construction 3f LCD alternating shutterelement  4 Beam splitter 4a, b, c Beam splitter  5 Disk 5a Semicirculararea 5b Remaining area of disk 5 5c Circular segment areas 5d  6 Axisfor disk  7 Central axis 7a, b Central axis  8 Main objective  9Electronic image recording device 10 Display 10a Display 11a, b Mirror12a, b, c Adjusting device 13 Zoom 14a, b Motor 15 Reciprocating drive16 Feed line 17 Light source 18 Eyepiece 19 Deflecting mirror 20 Pushrod 21 Rigid mirror 22 Object 23a, b, a′, b′; c, d Plane plate 24Pivoting drive 25 Linkage 30 Lamellar mirror of 3e 31 Tube lens 32 33Magnificaticn optics 34 Arrows 35 Further mirror 36 Actuating drive 37Beams 38a, b Deflecting mirror 39 Retroprism 40 Balance weight 41 Planarwave 42 Partial waves 43 Result 44 Phase plate 50a, b Beam splitter dStereo base p Phase pin

The reference symbols listed in this list of reference symbols alsorelate to components of the mentioned and following PCT patentapplications based on CH1088/94-3 and 1090/94-1, which can preferably beused together with the present inventions.

What is claimed is:
 1. A stereomicroscope having an eyepiece beam path(1 c) and a beam splitter (4 a) for reflecting information from adisplay (10 a) into the eyepiece beam path (1 c), and having twoeyepiece beam paths (1 c and 1 d), each of which is assigned to one eye,the information being able to be reflected into both eyepiece beam paths(1 c and 1 d) via one beam splitter (4 a) each, wherein, between thedisplay (10 a) and the beam splitter (4 a), a second beam splitter isdesigned as a mechanooptical switching element (3) which can betransferred alternately from a reflective into a transmissive state, oneof the two states exposing the light path for one of the two eyepiecebeam paths (1 c) and the other state exposing a light path for the othereyepiece beam path (1 d), while blocking the light path for the first ofthe two.
 2. The stereomicroscope according to claim 1, wherein on thedisplay (10 a), alternately and synchronized with the switching element(3), in each case a right and a left frame in each case as a field (HB)or raster image (VB) of a stereo image pair is displayed.
 3. Thestereomicroscope according to claim 1, wherein the two first beam paths(1 a, 1 b), together with two second beam paths (2 a, 2 b), which areconnected to the first beam paths (1 a, 1 b) via first beam splitters (4a, 4 b), lie in one plane, the two second beam paths being deflected insuch a way that they are incident on the mechanooptical switchingelement (3) and are alternately fed to the display (10 a), depending onthe state of the switching element (3).
 4. A stereomicroscope,comprising: a display, two eyepiece beam paths, a first beam splitterfor reflecting information from the display into one of the eyepiecebeam paths and for passing the information into another of the eyepiecebeam paths, each of which is assigned to one eye, a rigid mirrordisposed between the display and a first main beam path, a second beamsplitter disposed between the rigid mirror and a first eyepiece along afirst of said two eyepiece beam paths and the first main beam path, athird beam splitter disposed between the first beam splitter and asecond eyepiece along a second of said two eyepiece beam paths and asecond main beam path, wherein said second and third beam splitterssuperimpose the image information from the display onto frames in thefirst and second main beam paths, and a rotatable aperture diaphragmdisposed between the rigid mirror and the second beam splitter having atleast one passing and at least one blocking region, which blocks eithera first secondary beam path defined from said second beam splitter tosaid rigid mirror or a second secondary beam path defined from saidthird beam splitter to said first beam splitter.
 5. The stereomicroscopeaccording to claim 4, wherein the display shows, alternately and insynchronism with the aperture diaphragm, a right and a left frame ineach case as a field (HB) or raster image (VB) of a stereoimage pair. 6.The stereomicroscope according to claim 4 wherein the two main beampaths, together with the two secondary beam paths, which are opticallycoupled to the main beam paths via the second and third beam splitters,lie in one plane, the two secondary beam paths being deflected in such away that they are incident on the first beam splitter and are fed to thedisplay alternately, depending on a state of the aperture diaphragm.